JP2005039698A - Digital still camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of pressure difference and temperature difference between a space between light transmission members and the outside. <P>SOLUTION: This digital still camera has first, second light transmission members arranged in a photographic optical path, an opening which transmits photographic light fluxes and a pressure sandwiching part 5A which is located at a peripheral part of the opening and pressure sandwiched to the outside of an effective region of the first, second light transmission members, a spacer which forms the space is provided between the effective regions of both light transmission members and air ducts 5d1 to 5d3, 5g1, 5g2 which pneumatically communicates the space and the outside are provided in the pressure sandwiching part 5A of the spacer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a digital still camera having at least two light transmission members in a photographing optical path that passes through a photographing lens and reaches an image pickup device.

  In many digital still cameras, an optical low-pass filter (hereinafter referred to as LPF) is arranged in front of an image pickup device such as a CCD, and the photographic light beam that has passed through the photographic lens passes through the LPF, and further the cover glass of the image pickup device unit is used. The light passes through and enters the light receiving surface of the image sensor. A space is formed between the LPF and the cover glass by a frame-shaped spacer, and the spacer is pressed between the LPF and the cover glass by an LPF pressing spring (for example, see Patent Document 1).

JP 2003-143448 A

  In Patent Document 1, the space between the LPF and the cover glass is a sealed space. If this space is a sealed space, the internal pressure of the space rises above the external pressure depending on the environmental temperature, and the pressure is reduced to the LPF. The LPF may be lifted against the urging force of the holding spring, and dust may be introduced into the space. In addition, condensation may occur on the LPF and the cover glass due to temperature changes inside and outside the space.

The digital still camera according to the present invention is located in the first and second light transmitting members disposed in the photographing optical path, the opening through which the photographing light flux is transmitted, and the periphery of the opening. And a spacer that forms a space between the effective regions of the two light transmitting members, and the space and the outside of the spacer are compressed air. An air passage that communicates is provided.
According to a second aspect of the present invention, the air passage has a bent portion or a meandering portion so that the air does not move linearly from the outside to the space.
In the invention of claim 3, the first projecting portion that is in close contact with the first light transmitting member is formed in the clamping portion of the spacer so as to surround the opening, and is in close contact with the first light transmitting member. The second projecting portion is provided so as to surround the first projecting portion, and the cut and the portion between the projecting portions provided in the first and second projecting portions constitute an air passage.
The invention according to claim 4 is provided by shifting the positions of the cut lines of the first and second protrusions.
The invention according to claim 5 is such that a groove is formed in a portion that reaches the space through the cut of the second protrusion, the portion between both protrusions, and the cut of the first protrusion.
According to a sixth aspect of the present invention, the groove has a crank shape.
In the invention of claim 7, the first projecting portion that is in close contact with the first light transmission member is formed on one surface of the clamping portion so as to surround the opening, and the other surface of the clamping portion. Is formed so that the second protrusion closely attached to the second light transmission member surrounds the opening and is displaced from the position of the first protrusion. A through-hole penetrating the part between the two protrusions on both sides constitutes an air passage.
According to an eighth aspect of the present invention, the spacer is made of an elastic body, and the first and second protrusions are compressed and deformed by the pinching pressure.

  According to the present invention, the space between the first and second light transmitting members is provided with an air passage in the space between the first and second light transmitting members so that the temperature difference and the pressure difference between the inside and outside of the space are eliminated. It is possible to prevent undesired lifting and condensation of the light transmitting member.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing the vicinity of an imaging unit of a digital still camera according to the present embodiment, and L indicates a photographing optical axis. A subject luminous flux that has passed through a photographing lens (not shown) passes through the opening of the shutter 1 from the left side in the figure, passes through an LPF 2 (optical low-pass filter), and reaches the image sensor 10. The imaging element 10 is formed by integrating a chip 11 such as a CCD and a cover glass 12 covering the front surface of the imaging element 10 with a package 13, and is mounted on the imaging substrate 3 and supported by the bracket 4. Reference numeral 20 denotes a camera body.
In the following description, the surface of each member that faces the front of the optical axis is referred to as the front surface, and the surface that faces the rear of the optical axis is referred to as the back surface.

  At the time of assembly, LPF 2 is placed on the surface side of cover glass 12 through spacer 5, and LPF 2 is elastically supported by pressing spring 7 through filter fixing frame 6. That is, the holding spring 7 has a shape as shown in FIG. 2, the left and right pressing portions 7 a are applied to the filter fixing frame 6, and the upper and lower mounting portions 7 b are screwed to the bracket 4 with screws, so that the pressing portion 7 a is elastically deformed. Then, the fixed frame 6 is pressed rearward (to the right in FIG. 1) to support the LPF 2. One of the LPF 2 and the cover glass 12 constitutes a first light transmission member, and the other constitutes a second light transmission member.

The spacer 5 will be described in detail with reference to FIGS.
The spacer 5 is provided to prevent the optical performance from deteriorating by providing the space SP (FIG. 7) between the effective regions of the LPF 2 and the cover glass 12 without directly contacting the LPF 2 and the cover glass 12. Further, by interposing the spacer 5, the distance between the light receiving surface of the image sensor 10 and the surface of the LPF 2 can be increased. When dust adheres to the surface of the LPF 2, it appears in the image. However, as the distance is longer, the image of the dust can be blurred and image deterioration can be suppressed.

  The spacer 5 has a substantially rectangular opening OP for transmitting the photographic light flux, and the peripheral portion 5A thereof is sandwiched between the LPF 2 and the ineffective area of the cover glass 12 by the urging force of the pressing spring 7. The space SP formed thereby is preferably a sealed space from the viewpoint of dust prevention. This is because if dust enters the space SP from the outside, it may adhere to the back surface of the LPF 2 or the cover glass 12 and cause image deterioration. Some single-lens reflex digital still cameras can clean the surface of the LPF 2 from the lens mount opening, but the back surface of the LPF 2 facing the space SP and the cover glass 12 cannot be cleaned by the user himself. .

  Therefore, it is necessary to improve the adhesion between the LPF 2 and the spacer 5 and the cover glass 12 and the spacer 5 so that dust does not enter the space SP as much as possible. For this reason, the spacer 5 is made of rubber. Projecting lip portions 5a, 5b, and 5c are integrally formed so as to surround the opening OP in the pressing portion 5A that is pressed between the LPF 2 and the cover glass 12. In particular, the lip portion on the surface side in contact with the LPF 2 has a double structure of the outer lip portion 5a and the inner lip portion 5b. Is formed. The outer portion 5B of the pinching portion 5A is thick to ensure rigidity.

  The lip portions 5 a to 5 c are crushed (compressed and deformed) when the spacer 5 is sandwiched between the LPF 2 and the cover glass 12, and strongly adhere to the LPF 2 and the cover glass 12 by their elastic force. As a result, the close contact portion is not lifted and a gap is not generated, and the dust intrusion preventing effect is improved.

However, if the space SP is a completely sealed space, a temperature difference or a pressure difference may occur inside and outside the space SP. That is, the equation of state of gas PV = KT
However, if P is a pressure, V is a volume, K is a constant, and T is a temperature, the volume V is constant when the space SP is a sealed space. The differential pressure with the space increases. For this reason, there is a risk that the internal pressure P of the space will rise against the biasing force of the holding spring 7 at a high temperature, and if the spring force of the holding spring 7 is increased to prevent this, the assembly property deteriorates, There arises a space problem due to an increase in the size of the spring and a cost problem due to the use of an expensive spring material. Another problem is that condensation may occur on the LPF 2 and the cover glass 12 due to a temperature difference between the inside and outside of the space SP, which may hinder photographing.

  In the present embodiment, in order to solve the above-described problem, the space SP is not a completely sealed space, but is communicated with the outside space in the air. However, since there is a risk of dust entering from the outside if it is simply communicated, it has been devised to suppress it as much as possible.

  As can be seen from FIG. 3, the outer lip 5a does not surround the opening SP over the entire circumference, but is provided with cuts 5g1 at two central portions of the long side portion. On the other hand, the inner lip portion 5b is provided with a total of four cuts 5g2 one by one near the corner of the short side portion. As can be seen from FIGS. 4 to 6, a groove 5d1 reaching the outer thick portion 5b is formed in the cut portion of the outer lip portion 5a, and the inner and outer lip portion 5d2 is formed on the bottom surface of the groove 5d1. It is made into the groove shape one step lower so that it may become the same height. Further, a groove 5d3 reaching the opening OP is formed in the cut portion of the inner lip portion 5b, and the bottom surface of the groove 5d3 is set to the same height as the bottom surfaces of the grooves 5d1 and 5d2.

  In the assembled state, the cuts 5g1 and 5g2 and the grooves 5d1 to 5d3 serve as an air passage that connects the space SP and the outside in an air manner. The arrows in FIG. 5 indicate the air flow. As described above, the lip portions 5a and 5b are pressed and crushed against the back surface of the LPF 2, but the grooves 5d1 to 5d3 are present even when the lip portions 5a and 5b are completely crushed and the cut lines 5g1 and 5g2 are closed as shown in FIG. Therefore, an air passage is secured. For example, if the lip portion is formed slightly higher, an air passage can be secured by making a cut in the lip portion without providing the groove as described above.

  On the other hand, on the back surface of the spacer 5, since the lip portion 5c is not cut and has no groove, no air passage is formed. Since the lip portion 5c is formed between the surface side lip portions 5a and 5b, even if the groove 5d2 is provided on the surface side, the portion does not become thin, and the strength of the spacer 5 does not decrease.

  Since the space SP is in air communication with the outside in this way, there is no temperature difference or pressure difference inside or outside the space SP, and the pressure in the space can lift the spacer 5 without increasing the force of the holding spring 7. I will not let you. Further, no condensation occurs on the LPF 2 or the cover glass 12. Furthermore, since the air passage is not a simple linear shape but a crank shape, even if external dust enters from the groove 5d1, the possibility that it will reach the space SP is extremely low. Further, by making a plurality of cuts in the lip portion, the lip portion is easily crushed, and the effect of improving the assembly work efficiency can be obtained.

Here, the positions of the cuts 5g1 and 5g2 of the lip portions 5a and 5b are preferably determined in consideration of the following three conditions.
(1) In order to hold the LPF 2 stably, the deformation amount (crush amount) of the lip portion 5 due to the pressing of the pressing spring 7 needs to be uniform throughout. Since the presence or absence of cuts affects the degree of deformation of the lip, it is necessary to arrange a plurality of cuts point-symmetrically with respect to the center of the opening OP (corresponding to the photographing optical axis) in order to make the amount of deformation uniform. .
(2) From the viewpoint of preventing dust from entering the space SP, the air passage should be as long as possible and have at least two bent portions.
(3) Considering that dust has entered the space, image degradation caused by the dust becomes more conspicuous as it is closer to the center of the screen (photographing optical axis). Therefore, the cut 5g2 of the inner lip portion 5b, which is the dust intrusion position, is preferably close to the four corners as far as possible from the center of the space SP.
The example of FIG. 3 can be said to be the best mode that satisfies all the above three conditions. However, these conditions are not essential requirements of the invention.

  In addition, although the air passage was formed in the surface side of a spacer above, this may be formed in a back surface side, and may be formed in both surfaces. In addition, a double lip portion was provided, and a crank-shaped air passage was formed by shifting the position of the cut, but by providing three or more lip portions, the air passage can be made into a more complicated shape, It is possible to further enhance the dustproof effect. However, if the number of lip portions is large, a larger force is required when supporting by the presser spring 7, and it is necessary to determine the number of lip portions in consideration of this point. The air passage may not be crank-shaped, and may have a meandering portion such as an S-shaped curve. In any case, the dustproof performance can be enhanced by forming the shape in which air (dust) cannot move linearly over the space. Also, the number of air passages is not limited.

  The method of forming the air passage is not limited to that described above. For example, as shown in FIGS. 8 to 10, inner and outer lip portions 5 a 1, 5 a 2: 5 b 1, 5 b 2 are provided on the front and back of the clamping portion 5 A of the spacer 5. The air passage may be secured by a through hole 5h provided in the portion between the lip portions. In this case, the lip portions 5a2 and 5b1 can be omitted.

  The lip is not an essential requirement and may be a planar spacer. FIG. 11 shows an example in which a groove 5d3 is formed in the planar spacer 5 to form an air passage. The groove 5d3 has three bent portions and has high dustproof performance. The groove 5d3 may be provided on either or both of the front and back surfaces. Furthermore, the spacer is not limited to an elastic body, and may be plastic, for example. Further, the first and second light transmitting members are not limited to the LPF and the cover glass.

The sectional view which looked at the image pick-up part neighborhood of the digital still camera in one embodiment from the side. The perspective view which shows the presser spring for LPF pressurization. The figure which looked at the spacer from the LPF side. The expansion perspective view which shows the lip | rip part provided in the spacer, and the state of the cut | interruption. The figure explaining the air passage provided in the spacer, and the flow of air. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. The figure which expands and shows the principal part of FIG. The figure which looked at a part of spacer in other embodiments from the LPF side. The figure which looked at a part of spacer of FIG. 8 from the cover glass side. XX sectional drawing of FIG. The figure which shows the spacer in other embodiment.

Explanation of symbols

1 Shutter 2 Optical Low Pass Filter (LPF)
5 Spacer 5A Clamping part 5B Thick part 5a-5c Lip part 5d1-5d3 Groove 5g1, 5g2 Cut 5h Through hole 7 Holding spring 10 Image sensor 11 CCD chip 12 Cover glass OP Spacer opening SP Between LPF and cover glass Space

Claims (8)

First and second light transmissive members disposed in the photographing optical path;
An aperture for transmitting the imaging light beam, and a clamping portion located in the periphery of the aperture and clamped between the effective outer regions of the first and second light transmitting members, and an effective region of both the light transmitting members And a spacer that forms a space between them,
A digital still camera characterized in that an air passage for air communication between the space and the outside is provided in the clamping portion of the spacer. The digital still camera according to claim 1, wherein the air passage has a bent portion or a meandering portion so that air does not move linearly from the outside to the space. A first projecting portion that is in close contact with the first light transmitting member is formed at the clamping portion of the spacer so as to surround the opening, and is in close contact with the first light transmitting member. Two projecting portions are formed so as to surround the first projecting portion, and a cut and a portion between the projecting portions provided in the first and second projecting portions constitute the air passage. The digital still camera according to claim 1, characterized in that: 4. The digital still camera according to claim 3, wherein the first and second protrusions are provided with discontinuous positions. Grooves are formed in the pinching portion of the spacer at the cut of the second protruding portion, the portion between the two protrusions, and the portion of the first protruding portion that passes through the cut of the first protruding portion. The digital still camera according to claim 4. The digital still camera according to claim 5, wherein the groove has a crank shape. A first projecting portion that is in close contact with the first light transmission member is formed on one surface of the clamping portion of the spacer so as to surround the opening. On the surface, a second projecting portion that is in close contact with the second light transmitting member is formed so as to surround the opening and shifted from the position of the first projecting portion. 2. The digital still camera according to claim 1, wherein a through-hole penetrating a portion between the first and second protrusions on both sides constitutes the air passage. The digital still camera according to claim 3, wherein the spacer is made of an elastic body, and the first and second projecting portions are compressed and deformed by the clamping pressure.

Images